Splitboarding is unique in winter sports because it combines elements of skiing and snowboarding. A splitboard looks like a snowboard when fully assembled, but can be taken apart to be used as a pair of skis—the board is split lengthwise and each board half is a ski when separated. Splitboards typically include a ski binding interface and a splitboard binding interface such that a single pair of boot bindings is used to mount the rider's boots on either interface. Thus the rider can switch the bindings between a ski touring mode and a snowboard riding mode at will. In snowboard riding mode, with both feet spread apart on a board, the knee injuries that plague skiers are significantly reduced, but safety issues with ski touring mode remain.
In ski touring mode, there is a need for a fixed heel binding, for example when using climbing skins, when sidestepping up on steep slopes, and on a downhill ski run. A heel lock mechanism permits the rider to be more aggressive in turning and carving with the ski edges, improving performance. Wariakois in U.S. Pat. No. 5,984,324 suggested inserting a locking pin into the boot binding baseplate at the heel. However, skiing in this way, with no possible release, subjects the rider to risk of injury, such as an Achilles tendon tear or detachment. When the heel is locked to a ski, injury can result if the ski tip is levered toward the knee resulting in ankle hyperflexion, such that the heel tendon may be pulled from the calcaneus or torn in the hypovascular zone intermediate to the gastrocnemius. If the tendon is torn away with a bit of bone attached, the injury has a good prognosis, but soft tissue damage from a muscle or tendon tear typically takes a longer time to recover. Such tears may result in prolonged disability and the prospect of lifelong pain and weakness.
To reduce the safety hazard of locked heel skiing, skiers have developed alpine touring heel release technology. Breakaway mechanisms detach the boot at the heel when the torsional forces on the heel exceed a pre-selected threshold. The release threshold is adjusted according to the size, skill and physique of the user so as to prevent unnecessary release and sudden falls. A range of DIN settings is offered by each manufacturer and is dependent on a clamp that engages a hard boot worn by the rider.
Hard boot technology developed for skiing is not generally adapted for splitboarding because of the widespread preference for soft boots. Riders have increasingly opted to wear soft boots and use toe and ankle straps in combination with a heel cup to secure their leather boots to a baseplate. The baseplate is mounted on a toe pivot interface in ski touring mode or on a snowboard interface in snowboard ride mode. The baseplate can be rapidly interchanged between the two interfaces, and should also function for use with climbing bars and crampons. These complications dictate that any safety release mechanism for splitboarding is subject to a unique set of problems not encountered with alpine ski equipment.
Thus there is an unmet need for a splitboard boot binding means that will automatically disengage a rider's heel when the torsional force on the rider's foot exceed a safe level, but is otherwise stable and secure so as to avoid inadvertent and unnecessary disengagement. Also advantageous would be a release device that is readily reassembled and re-used after a release event, is easily engaged and disengaged with a ski pole or a gloved hand, is compatible with climbing bars and crampons, and—does not interfere with the essence of splitboarding, the capacity to easily switch between ski touring and snowboard ride modes.